Piaget Altiplano 900P

Amongst watchmakers, bragging rights rule, and none more so than the accolade of making the world's thinnest watch. It's a measure of skill, precision and ingenuity, and has been hotly contested since the dawn of watchmaking. Some of the biggest names in watchmaking—Jaeger-LeCoultre, Audemars Piguet, Patek Philippe— have traded blows with ever-thinner watches, all bitten by the desire to have that crowning jewel to their name. But in 2014, an even thinner watch was unveiled that wasn't made by any of those watchmakers, no—it was made by Piaget, and it's the Altiplano 900P at just 3.65mm.

Watch our video review of the Piaget Altiplano 900P G0A39111

To understand just how impressive the 900P really is, let's start by looking at something more ... normal. The Oris Sixty Five, for instance, is a straightforward automatic watch. It's a reasonable thickness by today's standards, with an off-the-shelf movement that's neither too large nor too small. The Sixty Five measures in at about 12mm. To get to the Altiplano's thickness, there's some way to go.

If we were to have a look at the Oris' de-cased movement, we'd see the biggest culprit of an automatic watch's size: the rotor weight. This is the part that spins when you move to keep your watch wound. Lose that and go fully manual wind and you'll save a few millimetres.

The world's thinnest watch uses some clever design to get to 3.65mm

Measure a manual wind watch and you get to about 8mm. We've saved 4mm over the automatic, but we've still got to lose over half the thickness again to catch up to the Altiplano. Alright, let's get ruthless. What if we took it a step further and measured the movement without the case? That'd us with five and a half millimetres.

Take off the hands and dial and we're at four millimetres. Nearly there.

At this point I'd like to remind you just how thick the Altiplano is—or rather, isn't. Three point six-five millimetres. Look at it. That's the case, hands, dial, movement, everything, and it still even has a decent two-day power reserve.

The caseback doubles as the baseplate, with the movement built straight on

So how exactly did Piaget manage this? A typical manual wind movement could be shaved a hair thinner, sure, but that still leaves the hands, dial, case. Turns out, Piaget's solution to making a whole watch the same thickness as a movement is pretty a clever one: make the watch out of the movement itself.

But what does this even mean? Well, first, the case back on the Altiplano isn't even a case back at all. It's actually the baseplate for the movement. Piaget builds the moving parts directly onto it, rather than doubling up with a baseplate and a case back, saving a few precious millimetres.

The orientation of the movement allows the dial to be recessed to save space

And the movement itself? 145 parts, all manufactured to fit within the height of the thickest component, the balance wheel. The thinnest component is just a tenth of a millimetre. That's the literal thickness of a human hair.

The movement, being so compact, allows for the next space-saving measure: the dial. With the wheels arranged around the edge, the dial and hands can be recessed off-centre into the empty space left behind, which in turn allows the bezel and crystal to sit lower down, screwed directly to the case back.

The result is a watch unmatched for slenderness

Sit the Altiplano side by side with that Oris and the technical mastery really becomes apparent. You could fit three 900Ps into the Oris and still have just over a millimetre to spare. That's quite a lot by Piaget's standards.

Piaget doesn't give too much away when it comes to the manufacturing process of the Altiplano 900P. This watch has been in the making since 1957, so it's safe to say that it's only been possible thanks to modern technology. And that's a good thing—it shows that watchmaking still has a lot to give, a lot of surprises left up its sleeve. It's especially important for Piaget, because it only took two years—a flash in watchmaking time—for Jaeger-LeCoultre to snatch the crown back again, beating the record by a paper-thin 0.05mm. I can't wait to see what's coming next.